Asymmetric Chelated Claisen Rearrangements in the Presence of Chiral Ligands—Scope and Limitations
作者:Uli Kazmaier、Heike Mues、Achim Krebs
DOI:10.1002/1521-3765(20020415)8:8<1850::aid-chem1850>3.0.co;2-q
日期:2002.4.15
Claisen rearrangements of glycine crotyl ester enolates in the presence of chelating metal salts and chiral ligands provide ,-unsaturated amino acids in a highly stereoselective fashion. Best results are obtained with electron withdrawing protecting groups, isopropylates of aluminum and magnesium, and the cinchona alkaloids as chiral ligands. While the use of quinine gives rise to the (2R)-configured
在螯合金属盐和手性配体的存在下,甘氨酸巴豆基酯烯醇酸酯的克莱森重排以高度立体选择性的方式提供了-不饱和氨基酸。用吸电子保护基,铝和镁的异丙基化物以及金鸡纳生物碱作为手性配体可获得最佳结果。虽然奎宁的使用产生了(2R)-构型的氨基酸,但是奎尼丁提供了相反的对映异构体。通过简单地改变反应条件,仅使用一种手性配体也可以得到不同的对映异构体。给出了反应的立体化学结果的机械原理,这由若干实验支持。